DBSCAN (Density-Based Spatial Clustering of Applications with Noise) is a data clustering algorithm It is a density-based clustering algorithm because it finds a number of clusters starting from the estimated density distribution of corresponding nodes.

It starts with an arbitrary starting point that has not been visited.

This point’s epsilon-neighborhood is retrieved, and if it contains sufficiently many points, a cluster is started. Then, a new unvisited point is retrieved and processed, leading to the discovery of a further cluster or noise. DBSCAN requires two parameters: epsilon (eps) and the minimum number of points required to form a cluster (minPts). If a point is found to be part of a cluster, its epsilon-neighborhood is also part of that cluster.

I implemented the pseudo code from DBSCAN wiki page:

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DBSCAN(D, eps, MinPts) C = 0 for each unvisited point P in dataset D mark P as visited N = getNeighbors (P, eps) if sizeof(N) < MinPts mark P as NOISE else C = next cluster expandCluster(P, N, C, eps, MinPts) expandCluster(P, N, C, eps, MinPts) add P to cluster C for each point P' in N if P' is not visited mark P' as visited N' = getNeighbors(P', eps) if sizeof(N') >= MinPts N = N joined with N' if P' is not yet member of any cluster add P' to cluster C |